Typo in x11-toolkits/gtk30

[David Demelier]

Hello,

I'm not sure that gtk-3.0 appears in 1997 ;-).

# New ports collection makefile for:   gtk13
                                        ^^^^^
# Date Created:			28 Sep 1997
                                 ^^^^^^^^^^^
# Whom:				Vanilla I. Shu <vanilla at MinJe.com.TW>
#
# $FreeBSD: ports/x11-toolkits/gtk30/Makefile,v 1.251 2011/07/30 
09:20:20 kwm Exp $
#   $MCom: ports/x11-toolkits/gtk30/Makefile,v 1.35 2011/06/07 13:19:12 
kwm Exp $
#

Cheers,

-- 
David Demelier